1. Field of the Invention
The invention relates generally to photonic measurement instruments and, more particularly, to high-precision atomic absorption instruments.
2. Background Information
Atomic absorption instruments, such as spectrometers, are well known and are used in a variety of settings. The atomic absorption instruments of interest are high-precision systems that include precisely aligned optics that tightly couple measurement light, that is, light of an appropriate wavelength for absorption analysis, to samples. The high-precision systems also utilize additional light sources and associated optics to provide reference paths to determine and compensate for light intensities as well as correct for background absorption. The systems of interest utilize simultaneously operating measurement and reference light paths, as described in U.S. Pat. No. 6,222,626, which is incorporated herein in its entirety by reference.
As described in the patent, a precisely aligned configuration of mirrors and beam splitters is used to direct the light from the measurement and background correction light sources, for example, a hollow cathode lamp “HCL” and a Deuterium (D2) lamp, simultaneously to the start of each of the measurement path and the reference path. The measurement path then uses a further plurality of precisely aligned mirrors to couple the light to a sample within an atomizer and also direct light from the atomizer to a detector, while the reference path uses optical fibers to guide the light to the detector.
The atomizer operating in the atomic absorption spectrometer is commonly either a flame (nebulizer) or a furnace, such as a graphite tube. Certain atomic absorption spectrometers can operate with more than one type of atomizer, and include manually or automatically operated mechanical mechanisms that move one atomizer, for example, a flame chamber, out of the optical measurement path and move another atomizer, for example, a furnace, into the optical measurement path. The movement of the atomizers often necessitates a re-alignment of the precisely aligned configuration of minors and beam splitters that direct light to the measurement path and/or the further plurality of minors that tightly couple the light to the sample. The re-alignment of the optics is both time consuming and complex, and results in system downtime.
Other known systems operate the atomizers in tandem, which works well if collimated light sources, such as lasers, are used. With light sources such as the HCLs and D2 lamps, however, the light beams diverge over the extended measurement path, and the optics of the tandem system are therefore quite complex and costly.